1. Field of the Invention
This invention relates to applying a conformal metal coating to an electronic circuit component.
2. Description of the Related Art
Metallic thin film conformal coatings are used in a variety of micro-system components for environmental protection, thermal management, prevention of electrostatic discharge, and electromagnetic and radio frequency interference shielding. In many applications, the conformal coating needs to be applied only to the metallic electrical circuitry that is patterned on to a semiconductor or insulator substrate (e.g., in microelectronics). However, common methods for applying conformal coatings, such as dipping in liquid or vapor/spray deposition coat the entire component indiscriminately, thereby producing short-circuits between the patterns. As a result, these techniques are unsuitable for selectively depositing a metal coating on patterned circuitry, unless a patterned mask or an insulating layer is first applied to prevent coating of the regions between the circuits. To date, there is no straightforward methodology for mask-less deposition of a conformal metallic coating on patterned circuitry on a chip.
While electric fields can be utilized to induce long-range flow of liquid electrolytes (electrophoresis or electro-osmosis), short-range wicking of liquid metals (electro-wetting), motion of discrete liquid metal inclusions embedded in solids, or surface transport of matter between discrete droplets of liquid metals, long-range continuous flow of liquid metal streams due to an electric field has never been reported or utilized before.